Side mounted rear view mirrors on a vehicle, and especially on transport trucks, are exposed to rain, snow, dew, dirt, and road salt. Those mirrors are often smeared and dirty, partially blocking the driver's view of the traffic besides and behind his vehicle.
Furthermore, it is not always practical for a truck driver to stop and wipe the rear view mirrors as often as his vision therein becomes hazy, and unsafe for the operation of the vehicle. For those reasons, it is desirable to have wiper devices mounted on these mirrors, and operable from the cab of the vehicle.
Various efforts have been made in the past to provide wipers for the outside, side mounted rear view mirrors of trucks, trailer trucks and vehicles of the like. For example, U.S. Pat. No. 3,685,087 issued on Aug. 22, 1972 to M. B. Pittman, discloses a wiper mechanism incorporated inside the housing of a rear view mirror. In this invention, the wiper blade reciprocates in an up and down motion. The wiper blade is driven in this movement by an arm which extends from within the mirror housing, and which travels along one side of the mirror frame.
As another example, U.S. Pat. No. 3,968,537 issued on Jul. 13, 1976 to J. J. Wagenhofer, discloses a wiper assembly which is adaptable for use with most types of laterally supported truck mirrors without radical structural alteration to the mirror frame. The wiper drive mechanism comprises a reciprocating plunger activated by a crank wheel and a rotary motor. The mechanism is contained within a housing which is held on the top of the mirror by a clamping member. The wiper blade is driven from side to side of the mirror surface, by the reciprocating plunger.
As a further example, a Canadian Patent Application serial no. 2,039,933 filed on Oct. 9, 1992, by R. B. Patterson, has a pneumatic cylinder attached to the upper portion of the mirror frame. The pneumatic cylinder pulls and pushes the wiper blade across the glass of the mirror.
The foregoing examples are just a few representative examples of efforts of others to deal with the problem of cleaning outside side mounted rear view mirrors. Generally, the prior art devices have the shortcomings of having slots within the mechanism compartment whereby moisture, dirt and road salt may deteriorate the internal components of the drive mechanism. Likewise, freezing rain and snow may penetrate and harden inside the slot to obstruct the movement of the wiper blade.
Other inconveniences with prior art wiper drive modules of the type which is attached to the frame of the mirror, comprise the fact that the volume of the drive housing mounted on the top of the mirror frame creates a sightless area above each side mirror.
Moreover, prior art wiper drive modules of the latter type require precise and rigid positioning onto the mirror frame, such that the movement of the wiper blade remains parallel to the surface of the glass. Hence this type of drive module must be fastened to the mirror frame such that its ideal position relative to the surface of the mirror is maintained even when the mirror is adjusted to the preference of different truck drivers.
It is also customary for a truck driver to attach an auxiliary flat or convex mirror to his main side rear view mirror. The alternate view point provided thereby is particularly useful to monitor the rear end of the trailer during wide turns, or to periodically check the movement of a load such as wood logs or bulky machinery. The presence of these auxiliary mirrors renders the installation of prior art wiper modules yet more difficult.